The world's richest soccer club, Manchester United, has called off talks with U.S. sports tycoon Malcolm Glazer over his proposed offer for the team, but has left the door open for further discussions.

The debt-free club said it would not support a bid that involved taking on a large amount of debt to finance a takeover. It said it still had not had a definite offer from Glazer, but had held talks regarding the potential structure of any deal.

"The board has decided to inform all shareholders that it would regard an offer which it believes to be overly leveraged as not being in the best interests of the company," the firm said in a statement on Monday.

Shares in Manchester United were down 3.4 percent at 274 pence in morning trading.

Glazer, owner of American football's Tampa Bay Buccaneers, has built his stake in the British club to 28.11 percent in recent weeks, sparking speculation of a bid which could value it as much as 787 million pounds ($1.4 billion).

One analyst said Manchester United's refusal to accept a heavily-indebted offer established the club's first line of defence and put the onus on Glazer to come back with a concrete, financed bid.

HOSTILE FANS

Fans of the 126-year-old club have been hostile to Glazer because of reports he planned to put the team into debt to finance his takeover. This would mean spending the club's profits on paying interest on the loan, rather than players.

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Manchester United said on Monday it intended to have further talks with the Glazer family and other interested shareholders.

"As a duty to shareholders, the door is always open if Glazer wants to sit down and discuss anything," a source close to the company told Reuters.

Glazer needs the club to recommend any offer he makes, as his chances of accumulating the 90 percent of shares needed to take the club private were scuppered earlier this month when two major shareholders rejected 300 pence a share for their stake.

Irish racehorse owners John Magnier and J.P. McManus, a shade ahead of Glazer's holding with their 28.9 percent stake, pulled out of talks with the U.S. tycoon to sell their holdings and said there was no possibility of reviving talks.

The Observer newspaper reported at the weekend that a leaked document, purportedly drawn up by some of Glazer's advisers, said investment bank JP Morgan would not release 400 million pounds in loans unless Glazer gets a recommendation for his bid.

JP Morgan declined to comment on Monday.

Under British takeover rules, Glazer would have to launch a formal bid for the club if his stake rose to 30 percent.

(Additional reporting by Mathieu Robbins)